In the 600's early Muslims immediately split into two groups, the Sunnite and the Shiite. The largest group was the Sunnite. They believed that the leadership passes to caliphs (leaders of the Islamic community) selected from the Prophet Muhammad's tribe. On the other hand, the Shiites believed that the true leaders of Islam must descend from the family of Ali, who was Muhammad's cousin's son-in-law. Ali became caliph from 656-661. Even though both groups believe in different things,they both believe in the Five Pillars of Faith (basic requirements for Muslims).
Another Muslim group are the Sufi. They are said to be the mystical or outer circle group of Islamic faith. Their beliefs are along the same lines as the rest of the groups but they submit themselves to God in different ways.
Major Islamic Groups
In the 600's early Muslims immediately split into two groups, the Sunnite and the Shiite. The largest group was the Sunnite. They believed that the leadership passes to caliphs (leaders of the Islamic community) selected from the Prophet Muhammad's tribe. On the other hand, the Shiites believed that the true leaders of Islam must descend from the family of Ali, who was Muhammad's cousin's son-in-law. Ali became caliph from 656-661. Even though both groups believe in different things,they both believe in the Five Pillars of Faith (basic requirements for Muslims).

Muhammad the Prophet
http://middleeast.about.com/od/religionsectarianism/a/me070907sunnis.htmAnother Muslim group are the Sufi. They are said to be the mystical or outer circle group of Islamic faith. Their beliefs are along the same lines as the rest of the groups but they submit themselves to God in different ways.
http://www.uga.edu/islam/Sufism.html